An Organic Light-Emitting Diode (OLED) display is one of focuses in the field of researches on tablet displays at present, and the OLED display has the advantages of low energy consumption, a low production cost, self-luminescence, a wide angle of view, a high response speed, etc., compared with a liquid crystal display. At present, the OLED display has come to take the place of the traditional Liquid Crystal Display (LCD) in the field of flat panel displays such as mobile phones, PDAs and digital cameras, where the design of a pixel circuit is a core aspect in the OLED display, so the researches thereon are highly significant.
Unlike the LCD in which the brightness is controlled using stable voltage, the OLED is current-driven, so it needs to be controlled by stable current to emit light. Threshold voltage Vth of a driver transistor in the pixel circuit may be non-uniform due to reasons such as a fabrication process thereof, and aging of elements thereof, so that the current flowing through the OLEDs at the respective pixels may vary, thus resulting in non-uniform display brightness, which may degrade the display effect of the entire image.